misc: Make the GDB register cache accessible in various sized chunks.

Not all ISAs have 64 bit sized registers, so it's not always very convenient
to access the GDB register cache in 64 bit sized chunks. This change makes it
accessible in 8, 16, 32, or 64 bit chunks. The MIPS and ARM implementations
were working around that limitation by bundling and unbundling 32 bit values
into 64 bit values. That code has been removed.

7 files changed, 174 insertions, 213 deletions

diff --git a/src/arch/alpha/remote_gdb.cc b/src/arch/alpha/remote_gdb.cc
index 21464fda4..951a20982 100644
--- a/src/arch/alpha/remote_gdb.cc
+++ b/src/arch/alpha/remote_gdb.cc
@@ -1,4 +1,5 @@
 /*
+ * Copyright 2014 Google, Inc.
  * Copyright (c) 2002-2005 The Regents of The University of Michigan
  * All rights reserved.
  *
@@ -145,7 +146,7 @@ using namespace std;
 using namespace AlphaISA;
 
 RemoteGDB::RemoteGDB(System *_system, ThreadContext *tc)
-    : BaseRemoteGDB(_system, tc, KGDB_NUMREGS)
+    : BaseRemoteGDB(_system, tc, KGDB_NUMREGS * sizeof(uint64_t))
 {
     memset(gdbregs.regs, 0, gdbregs.bytes());
 }
@@ -211,23 +212,20 @@ RemoteGDB::getregs()
 {
     memset(gdbregs.regs, 0, gdbregs.bytes());
 
-    gdbregs.regs[KGDB_REG_PC] = context->pcState().pc();
+    gdbregs.regs64[KGDB_REG_PC] = context->pcState().pc();
 
     // @todo: Currently this is very Alpha specific.
-    if (PcPAL(gdbregs.regs[KGDB_REG_PC])) {
-        for (int i = 0; i < NumIntArchRegs; ++i) {
-            gdbregs.regs[i] = context->readIntReg(reg_redir[i]);
-        }
+    if (PcPAL(gdbregs.regs64[KGDB_REG_PC])) {
+        for (int i = 0; i < NumIntArchRegs; ++i)
+            gdbregs.regs64[i] = context->readIntReg(reg_redir[i]);
     } else {
-        for (int i = 0; i < NumIntArchRegs; ++i) {
-            gdbregs.regs[i] = context->readIntReg(i);
-        }
+        for (int i = 0; i < NumIntArchRegs; ++i)
+            gdbregs.regs64[i] = context->readIntReg(i);
     }
 
 #ifdef KGDB_FP_REGS
-    for (int i = 0; i < NumFloatArchRegs; ++i) {
-        gdbregs.regs[i + KGDB_REG_F0] = context->readFloatRegBits(i);
-    }
+    for (int i = 0; i < NumFloatArchRegs; ++i)
+        gdbregs.regs64[i + KGDB_REG_F0] = context->readFloatRegBits(i);
 #endif
 }
 
@@ -239,22 +237,22 @@ void
 RemoteGDB::setregs()
 {
     // @todo: Currently this is very Alpha specific.
-    if (PcPAL(gdbregs.regs[KGDB_REG_PC])) {
+    if (PcPAL(gdbregs.regs64[KGDB_REG_PC])) {
         for (int i = 0; i < NumIntArchRegs; ++i) {
-            context->setIntReg(reg_redir[i], gdbregs.regs[i]);
+            context->setIntReg(reg_redir[i], gdbregs.regs64[i]);
         }
     } else {
         for (int i = 0; i < NumIntArchRegs; ++i) {
-            context->setIntReg(i, gdbregs.regs[i]);
+            context->setIntReg(i, gdbregs.regs64[i]);
         }
     }
 
 #ifdef KGDB_FP_REGS
     for (int i = 0; i < NumFloatArchRegs; ++i) {
-        context->setFloatRegBits(i, gdbregs.regs[i + KGDB_REG_F0]);
+        context->setFloatRegBits(i, gdbregs.regs64[i + KGDB_REG_F0]);
     }
 #endif
-    context->pcState(gdbregs.regs[KGDB_REG_PC]);
+    context->pcState(gdbregs.regs64[KGDB_REG_PC]);
 }
 
 void
diff --git a/src/arch/arm/remote_gdb.cc b/src/arch/arm/remote_gdb.cc
index 86dd5a725..fce060311 100644
--- a/src/arch/arm/remote_gdb.cc
+++ b/src/arch/arm/remote_gdb.cc
@@ -1,4 +1,5 @@
 /*
+ * Copyright 2014 Google Inc.
  * Copyright (c) 2010, 2013 ARM Limited
  * All rights reserved
  *
@@ -160,7 +161,8 @@ using namespace std;
 using namespace ArmISA;
 
 RemoteGDB::RemoteGDB(System *_system, ThreadContext *tc)
-    : BaseRemoteGDB(_system, tc, MAX_NUMREGS), notTakenBkpt(0), takenBkpt(0)
+    : BaseRemoteGDB(_system, tc, GDB_REG_BYTES),
+      notTakenBkpt(0), takenBkpt(0)
 {
 }
 
@@ -207,62 +209,50 @@ RemoteGDB::getregs()
 
     if (inAArch64(context)) {  // AArch64
         // x0-x31
-        for (int i = 0; i < 32; ++i) {
-            gdbregs.regs[REG_X0 + i] = context->readIntReg(INTREG_X0 + i);
-        }
+        for (int i = 0; i < 32; ++i)
+            gdbregs.regs64[GDB64_X0 + i] = context->readIntReg(INTREG_X0 + i);
         // pc
-        gdbregs.regs[REG_PC_64] = context->pcState().pc();
+        gdbregs.regs64[GDB64_PC] = context->pcState().pc();
         // cpsr
-        gdbregs.regs[REG_CPSR_64] = context->readMiscRegNoEffect(MISCREG_CPSR);
+        gdbregs.regs64[GDB64_CPSR] =
+            context->readMiscRegNoEffect(MISCREG_CPSR);
         // v0-v31
-        for (int i = 0; i < 32; ++i) {
-            gdbregs.regs[REG_V0 + 2 * i] = static_cast<uint64_t>(
-                context->readFloatRegBits(i * 4 + 3)) << 32 |
-                    context->readFloatRegBits(i * 4 + 2);
-            gdbregs.regs[REG_V0 + 2 * i + 1] = static_cast<uint64_t>(
-                context->readFloatRegBits(i * 4 + 1)) << 32 |
-                    context->readFloatRegBits(i * 4 + 0);
+        for (int i = 0; i < 128; i += 4) {
+            int gdboff = GDB64_V0_32 + i;
+            gdbregs.regs32[gdboff + 0] = context->readFloatRegBits(i + 2);
+            gdbregs.regs32[gdboff + 1] = context->readFloatRegBits(i + 3);
+            gdbregs.regs32[gdboff + 2] = context->readFloatRegBits(i + 0);
+            gdbregs.regs32[gdboff + 3] = context->readFloatRegBits(i + 1);
         }
     } else {  // AArch32
         // R0-R15 supervisor mode
-        // arm registers are 32 bits wide, gdb registers are 64 bits wide two
-        // arm registers are packed into one gdb register (little endian)
-        gdbregs.regs[REG_R0 + 0] = context->readIntReg(INTREG_R1) << 32 |
-            context->readIntReg(INTREG_R0);
-        gdbregs.regs[REG_R0 + 1] = context->readIntReg(INTREG_R3) << 32 |
-            context->readIntReg(INTREG_R2);
-        gdbregs.regs[REG_R0 + 2] = context->readIntReg(INTREG_R5) << 32 |
-            context->readIntReg(INTREG_R4);
-        gdbregs.regs[REG_R0 + 3] = context->readIntReg(INTREG_R7) << 32 |
-            context->readIntReg(INTREG_R6);
-        gdbregs.regs[REG_R0 + 4] = context->readIntReg(INTREG_R9) << 32 |
-            context->readIntReg(INTREG_R8);
-        gdbregs.regs[REG_R0 + 5] = context->readIntReg(INTREG_R11) << 32|
-            context->readIntReg(INTREG_R10);
-        gdbregs.regs[REG_R0 + 6] = context->readIntReg(INTREG_SP) << 32 |
-            context->readIntReg(INTREG_R12);
-        gdbregs.regs[REG_R0 + 7] = context->pcState().pc() << 32        |
-            context->readIntReg(INTREG_LR);
+        gdbregs.regs32[GDB32_R0 + 0] = context->readIntReg(INTREG_R0);
+        gdbregs.regs32[GDB32_R0 + 1] = context->readIntReg(INTREG_R1);
+        gdbregs.regs32[GDB32_R0 + 2] = context->readIntReg(INTREG_R2);
+        gdbregs.regs32[GDB32_R0 + 3] = context->readIntReg(INTREG_R3);
+        gdbregs.regs32[GDB32_R0 + 4] = context->readIntReg(INTREG_R4);
+        gdbregs.regs32[GDB32_R0 + 5] = context->readIntReg(INTREG_R5);
+        gdbregs.regs32[GDB32_R0 + 6] = context->readIntReg(INTREG_R6);
+        gdbregs.regs32[GDB32_R0 + 7] = context->readIntReg(INTREG_R7);
+        gdbregs.regs32[GDB32_R0 + 8] = context->readIntReg(INTREG_R8);
+        gdbregs.regs32[GDB32_R0 + 9] = context->readIntReg(INTREG_R9);
+        gdbregs.regs32[GDB32_R0 + 10] = context->readIntReg(INTREG_R10);
+        gdbregs.regs32[GDB32_R0 + 11] = context->readIntReg(INTREG_R11);
+        gdbregs.regs32[GDB32_R0 + 12] = context->readIntReg(INTREG_R12);
+        gdbregs.regs32[GDB32_R0 + 13] = context->readIntReg(INTREG_SP);
+        gdbregs.regs32[GDB32_R0 + 14] = context->readIntReg(INTREG_LR);
+        gdbregs.regs32[GDB32_R0 + 15] = context->pcState().pc();
 
         // CPSR
-        gdbregs.regs[REG_CPSR]  = context->readMiscRegNoEffect(MISCREG_CPSR);
+        gdbregs.regs32[GDB32_CPSR] = context->readMiscRegNoEffect(MISCREG_CPSR);
 
         // vfpv3/neon floating point registers (32 double or 64 float)
-
-        gdbregs.regs[REG_F0] =
-            static_cast<uint64_t>(context->readFloatRegBits(0)) << 32 |
-            gdbregs.regs[REG_CPSR];
-
-        for (int i = 1; i < (NumFloatV7ArchRegs>>1); ++i) {
-            gdbregs.regs[i + REG_F0] =
-                static_cast<uint64_t>(context->readFloatRegBits(2*i)) << 32 |
-                context->readFloatRegBits(2*i-1);
-        }
+        for (int i = 0; i < NumFloatV7ArchRegs; ++i)
+            gdbregs.regs32[GDB32_F0 + i] = context->readFloatRegBits(i);
 
         // FPSCR
-        gdbregs.regs[REG_FPSCR] = static_cast<uint64_t>(
-            context->readMiscRegNoEffect(MISCREG_FPSCR)) << 32 |
-                context->readFloatRegBits(NumFloatV7ArchRegs - 1);
+        gdbregs.regs32[GDB32_FPSCR] =
+            context->readMiscRegNoEffect(MISCREG_FPSCR);
     }
 }
 
@@ -277,63 +267,50 @@ RemoteGDB::setregs()
     DPRINTF(GDBAcc, "setregs in remotegdb \n");
     if (inAArch64(context)) {  // AArch64
         // x0-x31
-        for (int i = 0; i < 32; ++i) {
-            context->setIntReg(INTREG_X0 + i, gdbregs.regs[REG_X0 + i]);
-        }
+        for (int i = 0; i < 32; ++i)
+            context->setIntReg(INTREG_X0 + i, gdbregs.regs64[GDB64_X0 + i]);
         // pc
-        context->pcState(gdbregs.regs[REG_PC_64]);
+        context->pcState(gdbregs.regs64[GDB64_PC]);
         // cpsr
-        context->setMiscRegNoEffect(MISCREG_CPSR, gdbregs.regs[REG_CPSR_64]);
+        context->setMiscRegNoEffect(MISCREG_CPSR, gdbregs.regs64[GDB64_CPSR]);
         // v0-v31
-        for (int i = 0; i < 32; ++i) {
-          context->setFloatRegBits(i * 4 + 3,
-                                   gdbregs.regs[REG_V0 + 2 * i] >> 32);
-          context->setFloatRegBits(i * 4 + 2,
-                                   gdbregs.regs[REG_V0 + 2 * i]);
-          context->setFloatRegBits(i * 4 + 1,
-                                   gdbregs.regs[REG_V0 + 2 * i + 1] >> 32);
-          context->setFloatRegBits(i * 4 + 0,
-                                   gdbregs.regs[REG_V0 + 2 * i + 1]);
+        for (int i = 0; i < 128; i += 4) {
+            int gdboff = GDB64_V0_32 + i;
+            context->setFloatRegBits(i + 2, gdbregs.regs32[gdboff + 0]);
+            context->setFloatRegBits(i + 3, gdbregs.regs32[gdboff + 1]);
+            context->setFloatRegBits(i + 0, gdbregs.regs32[gdboff + 2]);
+            context->setFloatRegBits(i + 1, gdbregs.regs32[gdboff + 3]);
         }
     } else {  // AArch32
         // R0-R15 supervisor mode
         // arm registers are 32 bits wide, gdb registers are 64 bits wide
         // two arm registers are packed into one gdb register (little endian)
-        context->setIntReg(INTREG_R0 , bits(gdbregs.regs[REG_R0 + 0], 31, 0));
-        context->setIntReg(INTREG_R1 , bits(gdbregs.regs[REG_R0 + 0], 63, 32));
-        context->setIntReg(INTREG_R2 , bits(gdbregs.regs[REG_R0 + 1], 31, 0));
-        context->setIntReg(INTREG_R3 , bits(gdbregs.regs[REG_R0 + 1], 63, 32));
-        context->setIntReg(INTREG_R4 , bits(gdbregs.regs[REG_R0 + 2], 31, 0));
-        context->setIntReg(INTREG_R5 , bits(gdbregs.regs[REG_R0 + 2], 63, 32));
-        context->setIntReg(INTREG_R6 , bits(gdbregs.regs[REG_R0 + 3], 31, 0));
-        context->setIntReg(INTREG_R7 , bits(gdbregs.regs[REG_R0 + 3], 63, 32));
-        context->setIntReg(INTREG_R8 , bits(gdbregs.regs[REG_R0 + 4], 31, 0));
-        context->setIntReg(INTREG_R9 , bits(gdbregs.regs[REG_R0 + 4], 63, 32));
-        context->setIntReg(INTREG_R10, bits(gdbregs.regs[REG_R0 + 5], 31, 0));
-        context->setIntReg(INTREG_R11, bits(gdbregs.regs[REG_R0 + 5], 63, 32));
-        context->setIntReg(INTREG_R12, bits(gdbregs.regs[REG_R0 + 6], 31, 0));
-        context->setIntReg(INTREG_SP , bits(gdbregs.regs[REG_R0 + 6], 63, 32));
-        context->setIntReg(INTREG_LR , bits(gdbregs.regs[REG_R0 + 7], 31, 0));
-        context->pcState(bits(gdbregs.regs[REG_R0 + 7], 63, 32));
+        context->setIntReg(INTREG_R0, gdbregs.regs32[GDB32_R0 + 0]);
+        context->setIntReg(INTREG_R1, gdbregs.regs32[GDB32_R0 + 1]);
+        context->setIntReg(INTREG_R2, gdbregs.regs32[GDB32_R0 + 2]);
+        context->setIntReg(INTREG_R3, gdbregs.regs32[GDB32_R0 + 3]);
+        context->setIntReg(INTREG_R4, gdbregs.regs32[GDB32_R0 + 4]);
+        context->setIntReg(INTREG_R5, gdbregs.regs32[GDB32_R0 + 5]);
+        context->setIntReg(INTREG_R6, gdbregs.regs32[GDB32_R0 + 6]);
+        context->setIntReg(INTREG_R7, gdbregs.regs32[GDB32_R0 + 7]);
+        context->setIntReg(INTREG_R8, gdbregs.regs32[GDB32_R0 + 8]);
+        context->setIntReg(INTREG_R9, gdbregs.regs32[GDB32_R0 + 9]);
+        context->setIntReg(INTREG_R10, gdbregs.regs32[GDB32_R0 + 10]);
+        context->setIntReg(INTREG_R11, gdbregs.regs32[GDB32_R0 + 11]);
+        context->setIntReg(INTREG_R12, gdbregs.regs32[GDB32_R0 + 12]);
+        context->setIntReg(INTREG_SP, gdbregs.regs32[GDB32_R0 + 13]);
+        context->setIntReg(INTREG_LR, gdbregs.regs32[GDB32_R0 + 14]);
+        context->pcState(gdbregs.regs32[GDB32_R0 + 7]);
 
         //CPSR
-        context->setMiscRegNoEffect(MISCREG_CPSR, gdbregs.regs[REG_CPSR]);
+        context->setMiscRegNoEffect(MISCREG_CPSR, gdbregs.regs32[GDB32_CPSR]);
 
         //vfpv3/neon floating point registers (32 double or 64 float)
-        context->setFloatRegBits(0, gdbregs.regs[REG_F0]>>32);
-
-        for (int i = 1; i < NumFloatV7ArchRegs; ++i) {
-            if (i%2) {
-                int j = (i+1)/2;
-                context->setFloatRegBits(i, bits(gdbregs.regs[j + REG_F0], 31, 0));
-            } else {
-                int j = i/2;
-                context->setFloatRegBits(i, gdbregs.regs[j + REG_F0]>>32);
-            }
-        }
+        for (int i = 0; i < NumFloatV7ArchRegs; ++i)
+            context->setFloatRegBits(i, gdbregs.regs32[GDB32_F0 + i]);
 
         //FPSCR
-        context->setMiscReg(MISCREG_FPSCR, gdbregs.regs[REG_FPSCR]>>32);
+        context->setMiscReg(MISCREG_FPSCR, gdbregs.regs32[GDB32_FPSCR]);
     }
 }
 
diff --git a/src/arch/arm/remote_gdb.hh b/src/arch/arm/remote_gdb.hh
index a6b2b9d35..423ba9d02 100644
--- a/src/arch/arm/remote_gdb.hh
+++ b/src/arch/arm/remote_gdb.hh
@@ -1,4 +1,5 @@
 /*
+ * Copyright 2014 Google, Inc.
  * Copyright (c) 2013 ARM Limited
  * All rights reserved
  *
@@ -45,6 +46,8 @@
 #ifndef __ARCH_ARM_REMOTE_GDB_HH__
 #define __ARCH_ARM_REMOTE_GDB_HH__
 
+#include <algorithm>
+
 #include "base/remote_gdb.hh"
 
 class System;
@@ -54,21 +57,26 @@ namespace ArmISA
 {
 
 // AArch32 registers with vfpv3/neon
-const int NUMREGS   = 41;  /* r0-r15, cpsr, d0-d31, fpscr */
-const int REG_R0 = 0;
-const int REG_F0 = 8;
-const int REG_CPSR  = 8;   /* bit 512 to bit 543  */
-const int REG_FPSCR = 40;  /* bit 2592 to bit 2623 */
+enum {
+    GDB32_R0 = 0,
+    GDB32_CPSR = 16,
+    GDB32_F0 = 17,
+    GDB32_FPSCR = 81,
+    GDB32_NUMREGS = 82
+};
 
 // AArch64 registers
-const int NUMREGS_64 = 98;  // x0-x31, pc, cpsr (64-bit GPRs)
-                            // v0-v31 (128-bit FPRs)
-const int REG_X0 = 0;
-const int REG_PC_64 = 32;
-const int REG_CPSR_64 = 33;
-const int REG_V0 = 34;
+enum {
+    GDB64_X0 = 0,
+    GDB64_PC = 32,
+    GDB64_CPSR = 33,
+    GDB64_V0 = 34,
+    GDB64_V0_32 = 2 * GDB64_V0,
+    GDB64_NUMREGS = 98
+};
 
-const int MAX_NUMREGS = NUMREGS_64;
+const int GDB_REG_BYTES = std::max(GDB64_NUMREGS * sizeof(uint64_t),
+                                   GDB32_NUMREGS * sizeof(uint32_t));
 
 class RemoteGDB : public BaseRemoteGDB
 {
diff --git a/src/arch/mips/remote_gdb.cc b/src/arch/mips/remote_gdb.cc
index c35f532a1..9c944fc59 100644
--- a/src/arch/mips/remote_gdb.cc
+++ b/src/arch/mips/remote_gdb.cc
@@ -1,4 +1,5 @@
 /*
+ * Copyright 2014 Google, Inc.
  * Copyright (c) 2010 ARM Limited
  * All rights reserved
  *
@@ -148,7 +149,7 @@ using namespace std;
 using namespace MipsISA;
 
 RemoteGDB::RemoteGDB(System *_system, ThreadContext *tc)
-    : BaseRemoteGDB(_system, tc, GdbNumRegs)
+    : BaseRemoteGDB(_system, tc, GdbNumRegs * sizeof(uint32_t))
 {
 }
 
@@ -181,31 +182,26 @@ RemoteGDB::getregs()
     // two MIPS registers are packed into one gdb register (little endian)
 
     // INTREG: R0~R31
-    for (int i = 0; i < GdbIntArchRegs; i++) {
-        gdbregs.regs[i] = pack(
-                context->readIntReg(i * 2),
-                context->readIntReg(i * 2 + 1));
-    }
+    for (int i = 0; i < GdbIntArchRegs; i++)
+        gdbregs.regs32[i] = context->readIntReg(i);
     // SR, LO, HI, BADVADDR, CAUSE, PC
-    gdbregs.regs[GdbIntArchRegs + 0] = pack(
-                context->readMiscRegNoEffect(MISCREG_STATUS),
-                context->readIntReg(INTREG_LO));
-    gdbregs.regs[GdbIntArchRegs + 1] = pack(
-                context->readIntReg(INTREG_HI),
-                context->readMiscRegNoEffect(MISCREG_BADVADDR));
-    gdbregs.regs[GdbIntArchRegs + 2] = pack(
-                context->readMiscRegNoEffect(MISCREG_CAUSE),
-                context->pcState().pc());
+    gdbregs.regs32[GdbIntArchRegs + 0] =
+        context->readMiscRegNoEffect(MISCREG_STATUS);
+    gdbregs.regs32[GdbIntArchRegs + 1] = context->readIntReg(INTREG_LO);
+    gdbregs.regs32[GdbIntArchRegs + 2] = context->readIntReg(INTREG_HI);
+    gdbregs.regs32[GdbIntArchRegs + 3] =
+        context->readMiscRegNoEffect(MISCREG_BADVADDR);
+    gdbregs.regs32[GdbIntArchRegs + 4] =
+        context->readMiscRegNoEffect(MISCREG_CAUSE);
+    gdbregs.regs32[GdbIntArchRegs + 5] = context->pcState().pc();
     // FLOATREG: F0~F31
-    for (int i = 0; i < GdbFloatArchRegs; i++) {
-        gdbregs.regs[GdbIntRegs + i] = pack(
-                context->readFloatRegBits(i * 2),
-                context->readFloatRegBits(i * 2 + 1));
-    }
+    for (int i = 0; i < GdbFloatArchRegs; i++)
+        gdbregs.regs32[GdbIntRegs + i] = context->readFloatRegBits(i);
     // FCR, FIR
-    gdbregs.regs[GdbIntRegs + GdbFloatArchRegs + 0] = pack(
-                context->readFloatRegBits(FLOATREG_FCCR),
-                context->readFloatRegBits(FLOATREG_FIR));
+    gdbregs.regs32[GdbIntRegs + GdbFloatArchRegs + 0] =
+        context->readFloatRegBits(FLOATREG_FCCR);
+    gdbregs.regs32[GdbIntRegs + GdbFloatArchRegs + 1] =
+        context->readFloatRegBits(FLOATREG_FIR);
 }
 
 /*
@@ -217,41 +213,27 @@ RemoteGDB::setregs()
 {
     DPRINTF(GDBAcc, "setregs in remotegdb \n");
 
-    // MIPS registers are 32 bits wide, gdb registers are 64 bits wide
-    // two MIPS registers are packed into one gdb register (little endian)
-
     // INTREG: R0~R31
-    for (int i = 0; i < GdbIntArchRegs; i++) {
-        if (i) context->setIntReg(i * 2,
-                unpackLo(gdbregs.regs[i]));
-        context->setIntReg(i * 2 + 1,
-                unpackHi(gdbregs.regs[i]));
-    }
+    for (int i = 1; i < GdbIntArchRegs; i++)
+        context->setIntReg(i, gdbregs.regs32[i]);
     // SR, LO, HI, BADVADDR, CAUSE, PC
     context->setMiscRegNoEffect(MISCREG_STATUS,
-                unpackLo(gdbregs.regs[GdbIntArchRegs + 0]));
-    context->setIntReg(INTREG_LO,
-                unpackHi(gdbregs.regs[GdbIntArchRegs + 0]));
-    context->setIntReg(INTREG_HI,
-                unpackLo(gdbregs.regs[GdbIntArchRegs + 1]));
+        gdbregs.regs32[GdbIntArchRegs + 0]);
+    context->setIntReg(INTREG_LO, gdbregs.regs32[GdbIntArchRegs + 1]);
+    context->setIntReg(INTREG_HI, gdbregs.regs32[GdbIntArchRegs + 2]);
     context->setMiscRegNoEffect(MISCREG_BADVADDR,
-                unpackHi(gdbregs.regs[GdbIntArchRegs + 1]));
+        gdbregs.regs32[GdbIntArchRegs + 3]);
     context->setMiscRegNoEffect(MISCREG_CAUSE,
-                unpackLo(gdbregs.regs[GdbIntArchRegs + 2]));
-    context->pcState(
-                unpackHi(gdbregs.regs[GdbIntArchRegs + 2]));
+        gdbregs.regs32[GdbIntArchRegs + 4]);
+    context->pcState(gdbregs.regs32[GdbIntArchRegs + 5]);
     // FLOATREG: F0~F31
-    for (int i = 0; i < GdbFloatArchRegs; i++) {
-        context->setFloatRegBits(i * 2,
-                unpackLo(gdbregs.regs[GdbIntRegs + i]));
-        context->setFloatRegBits(i * 2 + 1,
-                unpackHi(gdbregs.regs[GdbIntRegs + i]));
-    }
+    for (int i = 0; i < GdbFloatArchRegs; i++)
+        context->setFloatRegBits(i, gdbregs.regs32[GdbIntRegs + i]);
     // FCR, FIR
     context->setFloatRegBits(FLOATREG_FCCR,
-                unpackLo(gdbregs.regs[GdbIntRegs + GdbFloatArchRegs + 0]));
+        gdbregs.regs32[GdbIntRegs + GdbFloatArchRegs + 0]);
     context->setFloatRegBits(FLOATREG_FIR,
-                unpackHi(gdbregs.regs[GdbIntRegs + GdbFloatArchRegs + 0]));
+        gdbregs.regs32[GdbIntRegs + GdbFloatArchRegs + 1]);
 }
 
 void
diff --git a/src/arch/mips/remote_gdb.hh b/src/arch/mips/remote_gdb.hh
index b9a227607..157276dcf 100644
--- a/src/arch/mips/remote_gdb.hh
+++ b/src/arch/mips/remote_gdb.hh
@@ -1,4 +1,5 @@
 /*
+ * Copyright 2014 Google, Inc.
  * Copyright (c) 2007 The Regents of The University of Michigan
  * All rights reserved.
  *
@@ -42,11 +43,10 @@ namespace MipsISA
 {
 
     // The number of special regs depends on gdb.
-    // Two 32-bit regs are packed into one 64-bit reg.
-    const int GdbIntArchRegs = NumIntArchRegs / 2;
-    const int GdbIntSpecialRegs = 6 / 2;
-    const int GdbFloatArchRegs = NumFloatArchRegs / 2;
-    const int GdbFloatSpecialRegs = 2 / 2;
+    const int GdbIntArchRegs = NumIntArchRegs;
+    const int GdbIntSpecialRegs = 6;
+    const int GdbFloatArchRegs = NumFloatArchRegs;
+    const int GdbFloatSpecialRegs = 2;
 
     const int GdbIntRegs = GdbIntArchRegs + GdbIntSpecialRegs;
     const int GdbFloatRegs = GdbFloatArchRegs + GdbFloatSpecialRegs;
@@ -69,23 +69,6 @@ namespace MipsISA
 
         void clearSingleStep();
         void setSingleStep();
-
-      private:
-        uint64_t
-        pack(uint32_t lo, uint32_t hi)
-        {
-            return static_cast<uint64_t>(hi) << 32 | lo;
-        }
-        uint32_t
-        unpackLo(uint64_t val)
-        {
-            return bits(val, 31, 0);
-        }
-        uint32_t
-        unpackHi(uint64_t val)
-        {
-            return bits(val, 63, 32);
-        }
     };
 }
 
diff --git a/src/arch/sparc/remote_gdb.cc b/src/arch/sparc/remote_gdb.cc
index cafd1799f..778c20731 100644
--- a/src/arch/sparc/remote_gdb.cc
+++ b/src/arch/sparc/remote_gdb.cc
@@ -1,4 +1,5 @@
 /*
+ * Copyright 2014 Google, Inc.
  * Copyright (c) 2002-2005 The Regents of The University of Michigan
  * All rights reserved.
  *
@@ -143,7 +144,7 @@ using namespace std;
 using namespace SparcISA;
 
 RemoteGDB::RemoteGDB(System *_system, ThreadContext *c)
-    : BaseRemoteGDB(_system, c, NumGDBRegs), nextBkpt(0)
+    : BaseRemoteGDB(_system, c, NumGDBRegs * sizeof(uint64_t)), nextBkpt(0)
 {}
 
 ///////////////////////////////////////////////////////////
@@ -185,34 +186,35 @@ RemoteGDB::getregs()
     PSTATE pstate = context->readMiscReg(MISCREG_PSTATE);
 
     if (pstate.am) {
-        uint32_t *regs;
-        regs = (uint32_t*)gdbregs.regs;
-        regs[Reg32Pc] = htobe((uint32_t)pc.pc());
-        regs[Reg32Npc] = htobe((uint32_t)pc.npc());
+        gdbregs.regs32[Reg32Pc] = htobe((uint32_t)pc.pc());
+        gdbregs.regs32[Reg32Npc] = htobe((uint32_t)pc.npc());
         for (int x = RegG0; x <= RegI0 + 7; x++)
-            regs[x] = htobe((uint32_t)context->readIntReg(x - RegG0));
+            gdbregs.regs32[x] = htobe((uint32_t)context->readIntReg(x - RegG0));
 
-        regs[Reg32Y] = htobe((uint32_t)context->readIntReg(NumIntArchRegs + 1));
-        regs[Reg32Psr] = htobe((uint32_t)pstate);
-        regs[Reg32Fsr] = htobe((uint32_t)context->readMiscReg(MISCREG_FSR));
-        regs[Reg32Csr] = htobe((uint32_t)context->readIntReg(NumIntArchRegs + 2));
+        gdbregs.regs32[Reg32Y] =
+            htobe((uint32_t)context->readIntReg(NumIntArchRegs + 1));
+        gdbregs.regs32[Reg32Psr] = htobe((uint32_t)pstate);
+        gdbregs.regs32[Reg32Fsr] =
+            htobe((uint32_t)context->readMiscReg(MISCREG_FSR));
+        gdbregs.regs32[Reg32Csr] =
+            htobe((uint32_t)context->readIntReg(NumIntArchRegs + 2));
     } else {
-        gdbregs.regs[RegPc] = htobe(pc.pc());
-        gdbregs.regs[RegNpc] = htobe(pc.npc());
+        gdbregs.regs64[RegPc] = htobe(pc.pc());
+        gdbregs.regs64[RegNpc] = htobe(pc.npc());
         for (int x = RegG0; x <= RegI0 + 7; x++)
-            gdbregs.regs[x] = htobe(context->readIntReg(x - RegG0));
+            gdbregs.regs64[x] = htobe(context->readIntReg(x - RegG0));
 
-        gdbregs.regs[RegFsr] = htobe(context->readMiscReg(MISCREG_FSR));
-        gdbregs.regs[RegFprs] = htobe(context->readMiscReg(MISCREG_FPRS));
-        gdbregs.regs[RegY] = htobe(context->readIntReg(NumIntArchRegs + 1));
-        gdbregs.regs[RegState] = htobe(
+        gdbregs.regs64[RegFsr] = htobe(context->readMiscReg(MISCREG_FSR));
+        gdbregs.regs64[RegFprs] = htobe(context->readMiscReg(MISCREG_FPRS));
+        gdbregs.regs64[RegY] = htobe(context->readIntReg(NumIntArchRegs + 1));
+        gdbregs.regs64[RegState] = htobe(
             context->readMiscReg(MISCREG_CWP) |
             pstate << 8 |
             context->readMiscReg(MISCREG_ASI) << 24 |
             context->readIntReg(NumIntArchRegs + 2) << 32);
     }
 
-    DPRINTF(GDBRead, "PC=%#x\n", gdbregs.regs[RegPc]);
+    DPRINTF(GDBRead, "PC=%#x\n", gdbregs.regs64[RegPc]);
 
     // Floating point registers are left at 0 in netbsd
     // All registers other than the pc, npc and int regs
@@ -229,14 +231,14 @@ void
 RemoteGDB::setregs()
 {
     PCState pc;
-    pc.pc(gdbregs.regs[RegPc]);
-    pc.npc(gdbregs.regs[RegNpc]);
+    pc.pc(gdbregs.regs64[RegPc]);
+    pc.npc(gdbregs.regs64[RegNpc]);
     pc.nnpc(pc.npc() + sizeof(MachInst));
     pc.upc(0);
     pc.nupc(1);
     context->pcState(pc);
     for (int x = RegG0; x <= RegI0 + 7; x++)
-        context->setIntReg(x - RegG0, gdbregs.regs[x]);
+        context->setIntReg(x - RegG0, gdbregs.regs64[x]);
     // Only the integer registers, pc and npc are set in netbsd
 }
 
diff --git a/src/base/remote_gdb.hh b/src/base/remote_gdb.hh
index 8fab556f3..ef414f09b 100644
--- a/src/base/remote_gdb.hh
+++ b/src/base/remote_gdb.hh
@@ -1,4 +1,5 @@
 /*
+ * Copyright 2014 Google, Inc.
  * Copyright (c) 2002-2005 The Regents of The University of Michigan
  * All rights reserved.
  *
@@ -36,6 +37,7 @@
 #include <map>
 
 #include "arch/types.hh"
+#include "base/intmath.hh"
 #include "base/pollevent.hh"
 #include "base/socket.hh"
 #include "cpu/pc_event.hh"
@@ -136,16 +138,25 @@ class BaseRemoteGDB
     class GdbRegCache
     {
       public:
-        GdbRegCache(size_t newSize) : regs(new uint64_t[newSize]), size(newSize)
+        GdbRegCache(size_t newSize) :
+            regs64(new uint64_t[divCeil(newSize, sizeof(uint64_t))]),
+            size(newSize)
         {}
         ~GdbRegCache()
         {
-            delete [] regs;
+            delete [] regs64;
         }
 
-        uint64_t * regs;
+        union {
+            uint64_t *regs64;
+            uint32_t *regs32;
+            uint16_t *regs16;
+            uint8_t *regs8;
+            void *regs;
+        };
+        // Size of cache in bytes.
         size_t size;
-        size_t bytes() { return size * sizeof(uint64_t); }
+        size_t bytes() { return size; }
     };
 
     GdbRegCache gdbregs;